Abstract
IGFBP-3 and IGFBP-6 were used to study whether both IGF I and IGF II play a role in auto-/paracrine stimulation of rat osteoblast growth. Both IGFBPs decreased basal DNA synthesis in neonatal rat calvaria cells but with different potencies. Consistent with their IGF binding affinities, IGFBP-3 blocked both IGF I- and IGF II-stimulated DNA synthesis, whereas IGFBP-6 preferentially blocked IGF II-stimulated DNA synthesis. These inhibitory effects of the two IGFBPs can be fully explained by the sequestration of IGFs. Because IGFBP-6 preferentially binds IGF II and is much less potent than IGFBP-3 in decreasing basal DNA synthesis in calvaria cells, IGF I but not IGF II appears to be an important auto-/paracrine stimulator of DNA synthesis.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Animals, Newborn
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Carrier Proteins / metabolism
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Carrier Proteins / pharmacology*
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Cell Line
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DNA / biosynthesis*
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DNA / drug effects
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Humans
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Insulin-Like Growth Factor Binding Protein 6
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Insulin-Like Growth Factor Binding Proteins
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Insulin-Like Growth Factor I / analogs & derivatives
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Insulin-Like Growth Factor I / metabolism*
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Insulin-Like Growth Factor I / pharmacology
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Insulin-Like Growth Factor II / metabolism*
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Kinetics
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Osteoblasts / cytology
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Osteoblasts / drug effects
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Osteoblasts / metabolism*
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Rats
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Recombinant Proteins / metabolism
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Skull
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Thymidine / metabolism
Substances
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Carrier Proteins
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Insulin-Like Growth Factor Binding Protein 6
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Insulin-Like Growth Factor Binding Proteins
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Recombinant Proteins
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insulin-like growth factor I, Gln(3)-Ala(4)-Tyr(15)-Leu(16)-
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Insulin-Like Growth Factor I
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Insulin-Like Growth Factor II
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DNA
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Thymidine